Tunable high-frequency circuits



May 9, 1950 R. D. FRAcAssl TUNABLE HIGH-FREQUENCY CIRCUITS Filed May 14, 1945 3 Sheets-Sheet l /NVE/VTOR FRACASS/ BY Mwah, 2f. 7M

ATTORNEY May 9, 1950 R. D. FRAcAssl 2,506,955

TUNABLE HIGH-FREQUENCY CIRCUITS F'iled May 14, 1945 3 She`ets-Sheet 2 F/G. 2 F/G. 3

/Nl/ENTOR D. FRACASS/ @im 5, 7M

A fro/m5 v May 9, 1950 R. D. FRAcAssl TUNABLE HIGH-FREQUENCY CIRCUITS Filed May 14, 1945 3 Sheets-Sheet 5 1 /NVENTOR R, D. FRACASS/ AT TORA/EV Patented May 9, 1950 UNI'IEDY STATES ?ATENT OFFICE TUNABLE HIGH-FREQUENCY CIRCUITS' Renato- D; Fracass, Chatham, N.v J., assigner, to. Belli Telephonehaboratories, Incorporated, New York; Y. a corporationof.` New York Application May 1'4",i 1945, Serial Nil..v 593,627

(Cl. B15-40') More specifically, objects. ofthis invention are' to increase'the tuning sensitivity of tunable magnetrons of the multiple cavity resonator type and to realize substantially straight line timing,l i. e. linear relationship between the resonant frequency of the resonators and position of the tuning member.

In. one illustrative v embodiment of the. invention,A

amagnetron comprises an anode or body member having a plurality of' bores extending therethrough and' dening substantially identical cavity resonators operatively associated with the,

anode-cathode region of the magnetron.

Inaccordance with one, feature of this invention, one or more annular grooves are provided'.

in one. face of the anode, or body member andv adjacent one end of the resonator dening bores, and means are: provided. which together with the bounding walls of the groove or grooves constitute variable capacitances in the resonator circuits. In one construction, this means comprises a metallic cylindrical member or members mounted so as. to: be displaced axially in either direction thereby toA vary the capacitances and, hence, the resonantv frequency of the resonators.

The Vinvention and the above noted and other features thereof will be understood more. clearly and fully from the following detailed description with reterence to the accompanying drawing,y in which;

Fig.v 1'. isr an end view of a magnetron illustrative of one embodiment of thisginvention, a portion being broken away to showdetails ofV con,- struction;

Fig. 2 is a view mainlyin section taken along line 2-2 of Fig. 1;

Fig. 3 is a side View of the device illustrated inFi-g; 1^-, portions being shown in'sectionto illustrate details of the tuning mechanism; and

Fig. 4 is an exploded perspective view showing details of the anode and of the tuning mechanism.

Referring now to the drawing, the magnetron therein illustrated comprises a circular metallic body or anode member I0, for example of copper, having an axial cylindrical bore II extending therethrough, the bounding surfaces of the bore constituting the anode segments of the device. The body I has also extending therethrough a 'ber Iii by screws 2i.

plurality of parallel, substantially identical bores.;

i12 equally spaced aboutthe bore I:I and communi-f eating therewith by radial slots I3, the bores: IZl dening' substantially identical cavityresonators.

" Disposedl coaxially within the bore: IIv is av cylin dricalcathode i4, which may beioic the equipotem. tial indirectly heated type and mounted' by lead'- ing-in conductors Itsealed invitreous. caps I6.V The caps It are sealed to metallic eyelets Ii'I"l in turn sealed to the body or anode member^` I0. As shown in Fig. l', the caps it and eyelets I'If may be protected by an insulating guard I8, for: example of glass, which is affixed, asibyfscrews'lm. to a bracket it' in turn secured to thebody memminals 22 to which the cathode leading-in'` conductors i5 are connected:

Power is taken from the magnetron byway of a coupling conductor 23 which extendsthroughl ametallic coupler 2d joined hermetically to. thev body Is and is sealed to al vitreous-stem 25' in turn sealed to the coupler 24.

One end ofv the anode or body member II). isi closed hermetically by a cover plate 2tv` joined to the body member iilas byv brazing. The other end is closed hermetically, in'- part `by an annularl plate 21 and in part by a diaphragm 28, which will bedescribed further hereinafter. The interior ofthe magnetron may be` highly evacuated by way of an exhaust coupling 23- sealed` to the body member Hl and closed', after the evacuation operation, by a vitreous cap Sil sealed thereto.

One face of the anode or body member Il! has-r therein an annular groove Si in which conductors' or straps 32 are disposed. These conductors or straps 32 form couplings between the sever-alf cavity resonators' and, as disclosed for exam-ple in the application Serial No. 529,619, filed' April 5f,`v 1944 of James B. Fisk, serve to assure oscillation of theresonators in a desired mode.

The other face of the anode or body' member- Ili is provided with a pair of, concentric annular grooves 33 intersected by the radial slots I3, the grooves. being coaxial with the central bore II. Extending into the grooves 33 and spaced from the bounding walls thereof are coaxial cylindrical. flanges 3G of a metallic, for example copper, plunger or tuning member 35, which as shown clearly in Fig. 4, is provided with a radial slot 38 to clear one of the cathode leading-in conductors I5. The tuning member is mounted by the diaphragm 28, which is dished as illustrated and affixed, as by brazing and a retainer ring 31, to the annular plate 21. Carried by the diaphragm and tuner member and ailixed thereto as The guard I8v carries ter-1 by solder washers, shown at 38 in Fig. 4, is a drive screw 39. The latter, when actuated as described presently, is displaced axially and drives the tuning member to move the ilanges 34 into or out of the grooves 33.

The flanges 34 together with the bounding walls of the grooves 33 define capacitances coupled to the cavityl resonators |2, the magnitude of the capacitances being determined by the extent to which the anges extend into the grooves. The tuner construction is substantially symmetrical electrically so that the resonant frequencies of the several cavity resonators are varied to the same extent, and of course simultaneously and in the same sense, as the flanges 34 are displaced in the grooves 33. Highly sensitive tuning, i. e. large change in frequency for small axial movement of the flanges 34, is obtained. Further, it has been found that a linear relationship obtains between the resonant frequency of the several cavity resonators and the position of the flanges so that substantially straight line tuning of the magnetron is realized.

`Very accurate and line tuning of the magnetron is attained by the use of a gear train for actuating the drive screw 39. In a particularly advantageous construction, illustrated in Figs. 1 and 3, the gear train comprises an inner race 40 to which a rst gear 4| is secured, as by screws 42, the race being threaded upon the screw 39 and having a channeled peripheral edge in which ball bearings 43 are disposed. The ball bearings are retained by an outer race 44 which is held in place by a resilient ring 45 ailixed to the plate 21 by a retainer 46 secured to the plate 21 by screws 47.

The gear 4| is driven by a second gear 48 which bears against a bearing washer 49 and is held in position by a retainer 59 aixed to the plate 21 by screws 5|, the retainer having a positioning hub 52 seated in a recess in the plate 21. The two gears 4| and 48 may be enclosed by a cover 53 fastened to the plate 21 by screws 54.

The gear 48 is driven in turn by a worm gear 55 which is locked to a shaft 56 carried by a bracket 5T having one end aixed to the body member 9 by two of the screws 2| and the other end afxed to this member by similar screws 58. A portion of the shaft 56 is threaded, as shown at 59 in Fig. 1, and carries a stop nut 66 which, by engagement with surfaces 6| or the bracket 51, serves to limit the number of turns of the shaft 59 in either direction. To facilitate manual rotation of the shaft 56 and, hence, tuning of the magnetron, a knurled knob 62 is provided on the shaft.

Although a Specific embodiment of this invention has been shown and described, it will be understood that it is but illustrative and that various modifications may be made therein without departing from the scope and spirit of this invention as defined in the appended claims.

What is claimed is:

,Y l. A magnetron comprising an anode body having a rst bore therein and a plurality of cavity resonator defining bores disposed about said rst bore, in communication therewith and extending from one face of the body, said body having in said one face an annular groove disposed intermediate said first bore and plurality of bores and removed therefrom, said groove being at regions of solely distributive capacitance, a cathode within said rst bore, a cylindrical tuning member mounted opposite and insertable into said groove, and means coupled thereto for moving said tuning member into and out of said groove.

2. A tunable high frequency circuit comprising a block of electrically conductive material having therein a iirst bore, a plurality of bores spaced from said first bore and a plurality of slots each extending from said first bore to a respective one of said plurality of bores, whereby said block constitutes a multicavity resonator system, said block having also therein a groove intersecting said slots intermediate said rst bore and said plurality of bores and removed therefrom, a conductive member adjacent said groove, and means coupled to said member for inserting it into said groove in spaced relation to the walls thereof to tune said system by alteration of capacitance solely.

3. An electron discharge device comprising an electrode member having a iirst bore therein, a plurality of bores spaced from said rst bore and a plurality of slots each extending from said first bore to a respective one of said plurality of bores, whereby said electrode member constitutes a multicavity resonator system, conductor straps in the region of said slots on one side of said electrode member only, said electrode member having a groove therein intersecting said slots at the other side thereof opposite said conductor straps, said groove being in a region of large distributed capacitance only, a conductive member adjacent said groove, and means coupled to said conductive member for adjustably inserting it into said groove in spaced relation to the walls thereof to vary the capacitance of said multicavity resonator system.

RENATO D. FRACASSI.

REFERENCES CITED The following references are of record in the iile of this patent:

UNITED STATES PATENTS Number Name Date 2,109,880 Dow Mar. 1, 1938 2,167,201 Dallenbach July 25, 1939 2,242,275 Varian May 20, 1941 2,251,085 Unk July 29, 1941 2,259,690 Hansen et al. Oct. 21, 1941 2,272,211 Kohler Feb. 10, 1942 2,408,234 Spencer Sept. 24, 1946 2,408,903 Biggs et al. Oct. 8, 1946 2,422,465 Bondley June 17, 1947 2,424,496 Nelson' July 22, 1947 2,444,080 Williams June 29,1948

FOREIGN PATENTS Number Country Date 509,102 Great Britain July 11, 1939 

